Highly regioselective nucleophilic/cycloaddition reactions of N-arylamino 1,3-diazabuta-1,3-dienes with α-nitrosostyrenes: synthesis of functionalised imidazoles and imidazole oxides

Abstract

The α-nitrosostyrenes 2, generated in situ from α-halogeno oximes, underwent regioselective cycloadditon/nucleophilic reactions with N-arylamino 1,3-diazabuta-1,3-dienes 1 leading to a mixture of imidazoles and cyclic nitrones shown to have structures 3 and 4, respectively, by X-ray crystallographic analysis. The structure 4 for cyclic nitrones was also supported by their 1,3-dipolar cycloaddition with dimethyl acetylenedicarboxylate (DMAD). The thermolysis of nitrones 4 gives imidazoles 3 via oxadiazine intermediates 6.